Datasheet

LTC3588-1
10
35881fa
OPERATION
The D0/D1 inputs can be switched while in regulation as
shown in Figure 3. If V
OUT
is programmed to a voltage with
a PGOOD falling threshold above the old V
OUT
, PGOOD will
transition low until the new regulation point is reached.
When V
OUT
is programmed to a lower voltage, PGOOD
will remain high through the transition.
Energy Storage
Harvested energy can be stored on the input capacitor or
the output capacitor. The wide input range takes advantage
of the fact that energy storage on a capacitor is proportional
to the square of the capacitor voltage. After the output
voltage is brought into regulation any excess energy is
stored on the input capacitor and its voltage increases.
When a load exists at the output the buck can effi ciently
transfer energy stored at a high voltage to the regulated
output. While energy storage at the input utilizes the high
voltage at the input, the load current is limited to what
the buck converter can supply. If larger loads need to be
serviced the output capacitor can be sized to support a
larger current for some duration. For example, a current
burst could begin when PGOOD goes high and would
continuously deplete the output capacitor until PGOOD
went low.
Figure 3. PGOOD Operation During D0/D1 Transition
TIME (ms)
0
V
OUT
VOLTAGE (V)
5
4
3
2
1
0
18161412108642
35881 F03
20
C
OUT
= 100µF, I
LOAD
= 100mA
V
OUT
D1=D0=0
PGOOD = LOGIC1
D1=D0=1 D1=D0=0